Rice and rise

Based on self-analysis, I'd say between two and three times as long.

Thanks, Avangi. Besides the length, is there any difference in how you pronounce the diphthong?
rise - / raiz /
rice - / rais /
I mean, when we pronounce a diphthong, the shape of the mouth changes: in this case from "a" to "i". I think "a" is at the back and "i" is at the front. Is it just that the transition from "a" to "i" is much quicker in / rais / ?

When I pronounce them, it's clearly the "ah" portion of the diphthong that suffers the loss. I'd say the anticipation of the quicker change in "rice" prevents me from lowering my tongue to the "full" "ah" position.

Thank you very much for the clear explanation. So, you open your mouth wider in "rise" than in "rice", right?

Yes. Both my jaw and my tongue drop a bit more.

I see. Thank you very much.

"Rice" has a "s" sound at the end which is unvoiced while "rise" has a "z" sound which is voiced.